Rydberg excitons in Cu2O microcrystals grown on a silicon platform

Stephan Steinhauer,Samuel Gyger,Birgit Kunert,André Mysyrowicz,Val Zwiller,Marijn A M Versteegh,Ali W Elshaari

doi:10.1038/s43246-020-0013-6

Abstract

Cuprous oxide (Cu2O) is a semiconductor with large exciton binding energy and significant technological importance in applications such as photovoltaics and solar water splitting. It is also a superior material system for quantum optics that enabled the observation of intriguing phenomena, such as Rydberg excitons as solid-state analogue to highly-excited atomic states. Previous experiments related to excitonic properties focused on natural bulk crystals due to major difficulties in growing high-quality synthetic samples. Here, the growth of Cu2O microcrystals with excellent optical material quality and very low point defect levels is presented. A scalable thermal oxidation process is used that is ideally suited for integration on silicon, demonstrated by on-chip waveguide-coupled Cu2O microcrystals. Moreover, Rydberg excitons in site-controlled Cu2O microstructures are shown, relevant for applications in quantum photonics. This work paves the way for the wide-spread use of Cu2O in optoelectronics and for the development of novel device technologies.

Highlights

Cuprous oxide (Cu2O) is a semiconductor with large exciton binding energy and significant technological importance in applications such as photovoltaics and solar water splitting
We present Cu2O growth by a scalable thermal oxidation process, which resulted in microcrystal structures with very low point defect and impurity levels
Thermal oxidation in a tube furnace resulted in Cu2O films with microcrystalline morphology, which can be seen in the top-view and cross-sectional scanning electron microscopy images

Summary

Introduction

Cuprous oxide (Cu2O) is a semiconductor with large exciton binding energy and significant technological importance in applications such as photovoltaics and solar water splitting. We present Cu2O growth by a scalable thermal oxidation process, which resulted in microcrystal structures with very low point defect and impurity levels. In single Cu2O microcrystals studied at cryogenic temperatures under continuous-wave excitation we demonstrate luminescence from excited np Rydberg states in lithographically site-controlled structures, exhibiting excellent agreement with a hydrogen-like quantum number dependence.

Results

Conclusion